MCP server "flow" fails to reconnect - HTTP 400 at flow.team

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code

### What's Wrong?

**Bug Description**
The "flow" MCP server (https://flow.team/ai/mcp) authenticates
successfully but fails to reconnect every time with HTTP 400.

**Steps to Reproduce**
1. Run /mcp
2. Select "flow" server
3. OAuth completes ("Authentication successful")
4. Claude Code shows: "Got new credentials, but reconnecting to
flow failed: HTTP 400 at https://flow.team"

**Tried (all failed with same error)**
- Clear authentication → re-authenticate
- Full restart of Claude Code
- claude --debug (no additional detail in log)

**Expected Behavior**
Server should connect and expose tools after successful auth.

**Actual Behavior**
"Status: failed", "Issue: SSE error: Non-200 status code (400)"
Auth shows as ✓ authenticated, but connection still fails.

**Environment**
- Claude Code version: 2.1.263
- OS: Windows
- Server URL: https://flow.team/ai/mcp
- Config location: local (.claude.json, project-scoped)

### What Should Happen?

**Bug Description**
The "flow" MCP server (https://flow.team/ai/mcp) authenticates
successfully but fails to reconnect every time with HTTP 400.

**Steps to Reproduce**
1. Run /mcp
2. Select "flow" server
3. OAuth completes ("Authentication successful")
4. Claude Code shows: "Got new credentials, but reconnecting to
flow failed: HTTP 400 at https://flow.team"

**Tried (all failed with same error)**
- Clear authentication → re-authenticate
- Full restart of Claude Code
- claude --debug (no additional detail in log)

**Expected Behavior**
Server should connect and expose tools after successful auth.

**Actual Behavior**
"Status: failed", "Issue: SSE error: Non-200 status code (400)"
Auth shows as ✓ authenticated, but connection still fails.

**Environment**
- Claude Code version: 2.1.263
- OS: Windows
- Server URL: https://flow.team/ai/mcp
- Config location: local (.claude.json, project-scoped)

### Error Messages/Logs

```shell

```

### Steps to Reproduce

**Bug Description**
The "flow" MCP server (https://flow.team/ai/mcp) authenticates
successfully but fails to reconnect every time with HTTP 400.

**Steps to Reproduce**
1. Run /mcp
2. Select "flow" server
3. OAuth completes ("Authentication successful")
4. Claude Code shows: "Got new credentials, but reconnecting to
flow failed: HTTP 400 at https://flow.team"

**Tried (all failed with same error)**
- Clear authentication → re-authenticate
- Full restart of Claude Code
- claude --debug (no additional detail in log)

**Expected Behavior**
Server should connect and expose tools after successful auth.

**Actual Behavior**
"Status: failed", "Issue: SSE error: Non-200 status code (400)"
Auth shows as ✓ authenticated, but connection still fails.

**Environment**
- Claude Code version: 2.1.263
- OS: Windows
- Server URL: https://flow.team/ai/mcp
- Config location: local (.claude.json, project-scoped)

### Claude Model

None

### Is this a regression?

Yes, this worked in a previous version

### Last Working Version

_No response_

### Claude Code Version

version: 2.1.263

### Platform

Anthropic API

### Operating System

macOS

### Terminal/Shell

Terminal.app (macOS)

### Additional Information

_No response_

Start by reproducing the /mcp flow with https://flow.team/ai/mcp and capture the reconnect request around the OAuth success; claude --debug and the reported SSE HTTP 400 are the available entry points. Check the Windows/macOS environment discrepancy while isolating the failure. Done means the authenticated flow server reconnects successfully and exposes its tools.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.